Common rail multi-cylinder fuel pump with independent pumping plunger extension

A fuel pump comprising:

• a barrel including a central bore having a longitudinal axis, wherein the barrel comprises a first section and a second section along the longitudinal axis;
• a plunger disposed in the central bore and movable along the longitudinal axis;
• a first coil spring guided by the first section of the barrel, wherein the first coil spring surrounds a first portion of the central bore;
• a second coil spring guided by the second section of the barrel, wherein the second coil spring surrounds a second portion of the central bore that is smaller than the first portion, and wherein the first section of the barrel is above the second section of the barrel;
• a spring retainer in contact with a tappet assembly, the spring retainer including a sidewall that engages a portion of the first coil spring;
• and
• an extender element coupled to the plunger and disposed above the spring retainer, the extender element including a sidewall that engages a portion of the second coil spring, wherein the extender element cooperates with the second coil spring to urge the plunger out of seized interference within the central bore.

A method in a fuel pump comprising:

• reciprocally moving a plunger within a central bore of a barrel along a longitudinal axis, wherein the barrel comprises a first section and a second section along the longitudinal axis;
• guiding a first coil spring by the first section of the barrel, wherein the first coil spring surrounds a first portion of the central bore;
• guiding a second coil spring by the second section of the barrel, wherein the second coil spring surrounds a second portion of the central bore that is smaller than the first portion, and wherein the first section of the barrel is above the second section of the barrel;
• biasing a spring retainer toward a tappet by the first coil spring, wherein the spring retainer includes a sidewall, a portion of the first coil spring being engaged by the sidewall;
• and
• biasing an extender element toward the tappet by the second coil spring, wherein the extender element is coupled to the plunger and disposed above the spring retainer, and wherein biasing the extender element toward the tappet urges the plunger out of seized interference within the central bore.

A fuel pump comprising:

• a barrel including a fuel drain port and a central bore having a longitudinal axis, wherein the barrel comprises a first section and a second section along the longitudinal axis,
• a plunger disposed partially in the central bore and movable along the longitudinal axis;
• a spring retainer;
• a first coil spring having a proximal end in contact with the first section of the barrel and a distal end in contact with the spring retainer to urge the spring retainer into engagement with a tappet assembly,
• and extender element coupled to the plunger and disposed above the spring retainer;
• a second coil spring having a proximal end in contact with the second section of the barrel and a distal end in contact with the extender element to urge the plunger toward the spring retainer, wherein the extender element includes a counter-bore to couple the extender element to the plunger, and wherein an end of the plunger spaces the extender element apart from the spring retainer;
• and
• wherein the fuel drain port is configured to drain excess fuel in an interface between the plunger and the central bore that is along a length of the plunger.